1    :  // Copyright 2012 Google Inc. All Rights Reserved.
   2    :  //
   3    :  // Licensed under the Apache License, Version 2.0 (the "License");
   4    :  // you may not use this file except in compliance with the License.
   5    :  // You may obtain a copy of the License at
   6    :  //
   7    :  //     http://www.apache.org/licenses/LICENSE-2.0
   8    :  //
   9    :  // Unless required by applicable law or agreed to in writing, software
  10    :  // distributed under the License is distributed on an "AS IS" BASIS,
  11    :  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  12    :  // See the License for the specific language governing permissions and
  13    :  // limitations under the License.
  14    :  //
  15    :  // Defines the ThreadStateBase and ThreadStateManager classes, which assists in
  16    :  // tracking and properly scavenging thread local resources owned by an agent
  17    :  // DLL as threads attach and detach from instrumented modules.
  18    :  
  19    :  #ifndef SYZYGY_AGENT_COMMON_THREAD_STATE_H_
  20    :  #define SYZYGY_AGENT_COMMON_THREAD_STATE_H_
  21    :  
  22    :  #include "base/synchronization/lock.h"
  23    :  #include "base/win/scoped_handle.h"
  24    :  #include "syzygy/agent/common/dlist.h"
  25    :  
  26  m :  namespace agent {
  27  m :  namespace common {
  28    :  
  29    :  // An abstract base class from which agent specific thread state objects
  30    :  // should be derived. This object maintains a handle to the thread on which
  31    :  // it was created. It is therefore expected that the thread state object will
  32    :  // be created by the thread on which it will be used.
  33  m :  class ThreadStateBase {
  34  m :   public:
  35    :    // Initialize a ThreadStateBase instance.
  36  m :    ThreadStateBase();
  37    :  
  38    :    // A virtual destructor to allow sub-classes to be safely deleted by the
  39    :    // ThreadStateManager.
  40  m :    virtual ~ThreadStateBase() = 0;
  41    :  
  42  m :   protected:
  43  m :    friend class ThreadStateManager;
  44    :  
  45    :    // The handle of the owning thread, used to scavenge thread data.
  46  m :    base::win::ScopedHandle thread_handle_;
  47    :  
  48    :    // The entry linking us into the manager's active_items_ or death_row_ lists.
  49  m :    LIST_ENTRY entry_;
  50    :  
  51  m :   private:
  52  m :    DISALLOW_COPY_AND_ASSIGN(ThreadStateBase);
  53  m :  };
  54    :  
  55    :  // A thread-safe class to manage the thread local state used by an agent.
  56  m :  class ThreadStateManager {
  57  m :   public:
  58    :    // Initialize a ThreadStateManager instance.
  59  m :    ThreadStateManager();
  60    :  
  61    :    // Destroys a ThreadStateManager instance.
  62  m :    ~ThreadStateManager();
  63    :  
  64    :    // Insert @p item into the list of active items.
  65  m :    void Register(ThreadStateBase* item);
  66    :  
  67    :    // Forcibly removes a thread state @p item from the active or death-row list,
  68    :    // as appropriate.
  69  m :    void Unregister(ThreadStateBase* item);
  70    :  
  71    :    // Transfer @p item from the list of active items to the death row list. This
  72    :    // does not delete @p item immediately.
  73  m :    void MarkForDeath(ThreadStateBase* item);
  74    :  
  75  m :   protected:
  76    :    // A helper method which gathers up any dead items from the death row list,
  77    :    // optionally transfers @p item from the list of active items to the death
  78    :    // row list, then delete all of the dead items. As a convenience, it takes
  79    :    // an optional bool param which will be set to true if there are any items
  80    :    // still being managed by this ThreadStateManager instance upon this
  81    :    // functions return.
  82  m :    void Scavenge(ThreadStateBase* item, bool* has_items_remaining);
  83    :  
  84    :    // Gathers all items which have been marked for death whose owning threads
  85    :    // have terminated into @p dead_items. These items can subsequently be deleted
  86    :    // using the Delete() method.
  87  m :    void GatherDeadItemsUnlocked(LIST_ENTRY* dead_items);
  88    :  
  89    :    // Deletes (using the delete operator) each item in @p dead_items.
  90  m :    static void DeleteDeadItems(LIST_ENTRY* dead_items);
  91    :  
  92    :    // Returns true if the thread which owns @p item has terminated.
  93  m :    static bool IsThreadDead(ThreadStateBase* item);
  94    :  
  95    :    // A lock protecting access to the lists of active and death_row entries.
  96  m :    base::Lock lock_;
  97    :  
  98    :    // A doubly-linked list of all thread local data items not yet marked for
  99    :    // death. Accessed under lock_.
 100  m :    LIST_ENTRY active_items_;
 101    :  
 102    :    // A doubly-linked list of all thread local data items currently marked for
 103    :    // death. Accessed under lock_.
 104  m :    LIST_ENTRY death_row_items_;
 105    :  
 106  m :   private:
 107  m :    DISALLOW_COPY_AND_ASSIGN(ThreadStateManager);
 108  m :  };
 109    :  
 110  m :  }  // namespace common
 111  m :  }  // namespace agent
 112    :  
 113    :  #endif  // SYZYGY_AGENT_COMMON_THREAD_STATE_H_